Experts who viewed the video clips speculated that Mehserle fired his gun because the officer had mistaken his handgun for a stun gun.

A BART police officer, idenitified as 27-year-old Johannes Mehserle, shot Grant on the Fruitvale station platform after responding to reports of men fighting on a train. Four officers had pulled Grant and a few other men out of the train. The victim was lying face down on the platform when he was shot. The shooting and events leading up to it were captured on amateur videos that have been broadcast on CBS 5 and other television outlets. Mehserle resigned from the transit agency shortly before he was supposed to be interviewed by investigators Wednesday. Mehserle's attorney did not respond to calls for comment. Grant's family in Hayward has filed a $25 million wrongful death claim against BART, and they want prosecutors to file criminal charges against Mehserle.
"There were racial slurs directed at the young men," family attorney John Burris said Thursday. "But I have no evidence that this particular officer (Mehserle) directed racial slurs towards Oscar Grant." Police have not classified the confrontation as a hate crime.
Some experts who viewed the video clips speculated that Mehserle fired his gun because he believed Grant had a deadly weapon, while others think the officer had mistakenly his handgun for a stun gun.